1. Field of the Invention
The present invention relates to an oscillation apparatus including a dielectric resonant element and to a communication apparatus using the oscillation apparatus.
2. Description of the Related Art
Heretofore, low-loss dielectric filters having improved frequency selectivity have been desired for effective use of frequency. In order to realize such characteristics, dielectric resonant elements having a high unloaded Q factor (hereinafter, simply referred to as “Qu”) are used.
The dielectric resonant elements included in oscillators are ones having a high Qu in order to reduce noise and stabilize the temperature characteristic.
Dielectric resonant elements using a TE01δ mode are effective as the dielectric resonant elements having a high Qu. An oscillator using the dielectric resonant element in the TE01δ mode is disclosed in Japanese Unexamined Patent Application Publication No. 2000-323923.
An oscillator that receives signals from broadcasting satellites (BSs) and signals from communications satellites (CSs) with a single converter is disclosed in Japanese Unexamined Patent Application Publication No. 09-162646. In order to receive two kinds of signals within different frequency bands, two local oscillators corresponding to the frequency bands are required. For example, the local oscillation frequency for BS broadcasting is 10.678 GHz and the local oscillation frequency for CS broadcasting is 11.200 GHz. Heretofore, one TE01δ single-mode resonator for the corresponding frequency has been used for every local oscillator; namely, two TE01δ single-mode resonators have been used.
Receiving two kinds of signals having different frequencies with a single converter can realize compact and low-cost receivers to some extent. However, since two separate oscillators are provided in the converter, it is impossible to drastically reduce the size and cost of the converter.